Modulating system



July 17, 1934. REPLQGLE 1,967,041

MODULATING SYSTEM Filed June 21, 1929 INVENTOR 0:45:27 5 7954 40645 A EERNEY i sion.

Patented July 17, 1934 UN T D- TA ES MODT ILATING SYSTEM Delbert E. Replogle, Newton,- Mass., assignor to Raytheon Production Corporation, Cambridge, Mass., a' corporation of Delaware Application June 21, 1929, Serial No. 372,603 7 Claims. (01. 1'786) This invention relates to modulating systems and in its broadest aspect discloses a system wherei'ntwo beams of light are so combined as to result in a modulated beam. In another aspect, this invention discloses a system wherein modulated electric currents are obtained in a novel and efi'icien't manner by the use of beams of light. v

In' general, .I' obtain modulated light by combining the output of a lamp which is flickering at a steady and predetermined rate with the output of another lamp whose iiickerings correspond in some manner .to predetermined variations of light reflecting conditions, energy or the like. Thus'the modulating light impulses might be those'occurring at regular intervals from a scanning disk in a television system and reflected in varying amounts from the object to be scanned. It is evident that by combining a beam of light flickering at a steady rate with such light as above that a modulated composite'light is .obtained which may be. used for a variety of pur-- poses. Such a modulated light beam could be recorded on a moving film for future'transmis- Sound could be similarly recorded in a modulated condition.

I prefer; however, to use my invention inconnection with well known systems for transmitting pictures or recording .soundby electrical meth-' T ods.

Inthe' ordinary systemsfor transmitting pictures. over wire, it is customary to scanan object and transform the reflected light impulses into; corresponding electrical impulses. This transformation is usually done in'a photo-electric cell.

Before suchinipuIs'es maybe transmitted over customary communication channels, it is highly desirable and in fact necessary that the impulses be translated into the frequency spectrum useful for commercial purposes. This translation is customarily accomplished by very powerfully amplifying the minute outputs of the photoelectric cell and modulating an oscillator. By my invention I am enabled to combine the original 45.". television impulses with other light impulses and obtain a modulated output which may immediately be amplified for transmission.

Among the advantages of such a procedure is the ease and fidelity with which such a modulated output is amplified. Since the modulating and modulated impulses are of the same order of magnitude as regards energy content, it is evident that the combination will not be accompanied by the distortion usually accompanying the modulation of powerful impulses by weak PAT-Eur OFFICE impulses. Furthermore, since the output of a photoelectric cell is practically linearly related to the intensity of light'falling thereon, it follows that the combination of the two impulses at thephotoelectric cell will be combined as a composite impulse in a much more faithful manner than is the case with an ordinary vacuum tube.

In addition, 'no elaborate equipment .will be necessary for the construction of a'high powered oscillator as is the case at present. With this invention, a comparatively, small powered vacuum tube may be useful for the production of a rapidly varying source of light. This, combined with'the television impulses, gives rise to currents which may be amplified'by ordinary amplifiers to as great a degree as may be found necessary.

Preferably though not necessarily, I employ the inductance type of lamp shown and described in Patent 8%,534 to Hewitt. Such a lamp may consistof a'sealed glass electrodeless container with one or'more gases or vapors at a reduced pressure. A coil carrying current at a .high frequency will cause such a lamp to glow withan intense light if placed within the turns of the coil. This light follows variations of electrical currentinstantaneously and faithfully. However, I may use any-other of the Well known types of lamps. capable of varying the light outputinstantaneously with variations in electrical input.

Referring to the drawing, the single figure shows the diagrammatic embodiment of my invention. Motor M drives a scanning disk D which intermittently allows a line beam of light from lamp'L to pass through the apertures in the disk to lens G and then tothe, object to be viewed. This light is reflected from the object to a photoelectric cell C. This cell has the property of transforming light impulses into corresponding electrical impulses. An oscillator O in conjunction with an inductance I and capacity C is shown as energizing an inductance lamp z. This inductance lamp is preferably provided with a reilector R which directs the light upon the object to be scanned.

It is evident that the beam of light from a varies in intensity in accordance with the variations of current in the oscillating circuit supplying it. The same would be true if the inductance type of lamp were replaced by any of the other well known types of lamps. Since as shown the beam of light from .2 is reflected from substantially the entire object scene to be transmitted, the amount of light in said beam after its reflection from said object scene will vary in accordcell C. It is clear that the electrical output of C represents the composite outputs of the two light beams. The output of C may be led to suitable amplifiers for final transmission by wire or radio to the customary television transmitting systems.

I claim:

1. A system for obtaining modulated electric currents corresponding to variations in light intensity, comprising a source of light, means for scanning an object to obtain variations of light from said source of light, another source of light, means for varying said other source at any desired frequency, additional means to cause the light from said other source to impinge upon substantially the entire area of said object to vary the intensity of light from said other source in accordance with the integrated light value of said image, the light from said sources being directed to combine the light impulses from said two sources, and means for translating said combined light impulses into electrical impulses.

2. A signalling system comprising a source of light, means for obtaining light impulses from said source corresponding to portions of an image to be transmitted, another source of light, means for varying the intensity of said source of light at a high frequency, additional means to cause the light from said other source to impinge upon substantially the entire area of said image to vary the intensity of the light from said other source in accordance with the integrated light value of said image, the light from said sources being directed to combine the light from said two sources and means for translating said combined lights into electrical impulses.

3. A signalling system comprising a source of light, means for obtaining light impulses from said source corresponding to an image to be transmitted, another source of light, means for varying the intensity of said other source of light i at a predetermined rate, additional means to cause the light from said other source to impinge upon substantially the entire area of said image to vary the intensity of the light from said other source in accordance with the integrated light a value of said image, the light from said sources being directed to combine said light impulses, a

photo-electric cell, means for amplifying the output of said photo-electrical cell and means for directly transmitting said amplified output.

4. A method for obtaining modulated electrical impulses corresponding to light variations which consists in rapidly varying the intensity of a source of light, varying the light from said source in accordance with the integrated light value of an image to be transmitted scanning an image to produce signal variations of light corresponding to elemental areas of said image combining this rapidly varying light with the signal variations of light corresponding to elemental areas of said image and translating said combined light variations into electrical variations.

5. In a television system, the method of transmitting image impulses, which comprises producing light impulses corresponding to elemental areas of an image, producing high frequency light from an oscillator, varying the light from said oscillator in accordance with the integrated light value of said image, combining the said light impulses to be transmitted with the light from said oscillator after being varied by said image, and translating said combined light impulses into 1 electrical impulses.

6. A system for obtaining modulated light which comprises a source of light varying at a predetermined rate from extinction to full brilliancy, additional means to cause the light from said 105 source to impinge upon substantially the entire area of an image to vary the intensity of the light from said source in accordance with the integrated light value of said image, another source of light, means for scanning said image to 110 obtain variations in light from said other source corresponding to elemental areas of said image, the light from said two sources after being varied by said image being directed to combine with one another.

7. A signal system comprising a source of light varying at a high frequency, means for directing said light upon substantially the entire area of an image to be transmitted, whereby said light is regulated in accordance with the integrated light 120 value of said image, a steady source of light, means for directing light from said source upon successive elemental areas of said image, whereby light variations corresponding to the light value of successive elemental areas of said image are 5 obtained, the light from both of said sources after being modified by said image being directed to combine with one another, and a photo-cell for converting said combined lights into electrical variations corresponding thereto.

DELBERT E. REPLOGLE. 

